Question

Which of the following substances give ${\text{H}}^{+}$ ions in aqueous solution?

• A. ${\text{H}}_3{\text{PO}}_4$
• B. ${\text{CH}}_3\text{COOH}$
• C. ${\text{H}}_2{\text{CO}}_3$
• D. ${\text{C}}_2{\text{H}}_5\text{OH}$

Answer 1

Answer: (A), (B), (C)

The correct options are
A ${\text{H}}_3{\text{PO}}_4$
B ${\text{CH}}_3\text{COOH}$
C ${\text{H}}_2{\text{CO}}_3$

Ionic compounds dissociate in an aqueous solution to form their respective cations and anions. Here, all the given options except ethanol (${\text{C}}_2{\text{H}}_5\text{OH}$) are ionic compounds. The table given below shows the cation and anion formed when these ionic compounds are dissolved in water.

$\begin{array}{ccc}\text{Acid}& \text{Cation}& \text{Anion}\\ \text{Phosphoric acid}\left({\text{H}}_3{\text{PO}}_4\right)& {\text{H}}^{\text{+}}& {\text{PO}}_{\text{4}}^{\text{3-}}\\ \text{Acetic acid}\left({\text{CH}}_{\text{3}}\text{COOH}\right)& {\text{H}}^{\text{+}}& {\text{CH}}_{\text{3}}{\text{COO}}^{-}\\ \text{Carbonic acid}\left({\text{H}}_{\text{2}}{\text{CO}}_{\text{3}}\right)& {\text{H}}^{\text{+}}& {\text{CO}}_{\text{3}}^{\text{2-}}\end{array}$

From the above table, it is evident that phosphoric acid, acetic acid and carbonic acid gives out ${\text{H}}^{+}$ ions when they are dissolved in water.

Ethanol consists of covalent bonds. In these bonds, the electrons are more attracted to the oxygen atoms of water molecules but it doesn't give ${\text{H}}^{+}$ ions in aqueous solution.